IL-10 producing CD8+ T cells in human infection with Leishmania guyanensis

Cytokines are increasingly recognized as important components of the cellular immune responses to intracellular pathogens. In this study, we analyzed the production of TGF-β, IL-10 and IFN-γ by PBMC of unexposed naïve subjects and LCL patients after stimulation with live Leishmania guyanensis (L.g.). We demonstrated that IFN-γ is produced in controls and LCL patients, IL-10 only in LCL patients and TGF-β only in naïve subjects. Furthermore, in naive subjects, neutralization of TGF-β induced IL-10 production. IL-10 produced in naïve subjects when TGF-β is neutralized or in LCL patients did not modify the IFN-γ production but inhibit reactive nitrogen species production. Analysis of the phenotype of IL-10 producing cells in naive subjects when TGF-β is neutralized clearly showed that they are memory CD45RA− CD8+ T cells. In LCL patients, IL-10 producing cells are both CD45RA− CD4 and CD8+ T cells. The role of these IL-10 producing CD8+ T cells in the development of the diseases should be carefully evaluated.